It is known in the art to incorporate in phosphorous compounds in polymeric resins. Thermal stabilization of polyesters has been reported in U.S. Pat. No. 3,609,118 to be attained by incorporating certain phosphines or certain phosphinic acid esters. Polycarbonate compositions containing minor amounts of phosphonite have been disclosed in U.S. Pat. No. 3,978,020. These compositions are said to exhibit improved thermal stability. Also known are polycarbonate compositions containing phosphites.
It has, however, long been recognized that such compositions, which contain these phosphorous compounds as additives, are susceptible to hydrolysis. Temperature and/or pressure accelerate this effect, evidenced by a decrease of the molecular weight. The degree of degradation may be determined and quantified by measurement of melt flow.
Corrective measures have been often sought.
The efficacy of oxazoline-containing additives in the context of polymeric resins, including polycarbonates, has been previously disclosed. Among the relevant documents, mention may be made of U.S. Pat. No. 4,895,897, which disclosed a polycarbonate containing thermoplastic molding composition having improved impact performance. The composition contains a functionalized elastomer which is the reaction product of (i) an ethylene elastomer having at least one reactive polar group and (ii) oxazoline-functionalized polystyrene. Surfaces with high gloss are said in U.S. Pat. No. 5,274,034 to characterize parts molded from a polycarbonate composition. This composition also contains aromatic polycarbonate with reactive carboxylic acid group and styrene-based polymer with repeating units containing pendant cyclic iminoether groups.
The polymers and oligomers of olefinically unsaturated hydrocarbons containing oxazolinyl end groups have been disclosed in U.S. Pat. No. 5,756,621 for their utility as compatibilizers in polymer blends. Also relevant is U.S. Pat. No. 4,590,241, which disclosed a compatible blend of thermoplastic resins. The blend contains a reactive polymer having repeating units containing pendant cyclic iminoether groups. That polymer is reacted to form a linkage and a compatible blend with a thermoplastic polymer containing a co-reactive group.